The invention relates to microelectropolishing techniques, and more particularly to a method for microelectropolishing a transmission electron microscopy nonhomogeneous multi-element compound foil.
Electropolishing may be broken down into two distinct processes, macroelectropolishing or smoothing wherein large scale asperities are removed, and microelectropolishing or brightening wherein smaller (less than 1 micron) irregularities are removed. In immersion or bath electropolishing, both processes take place. Macroelectropolishing occurs as anode material diffuses into the electrolyte from surface asperities due to the greater concentration gradient thereat. Macroelectropolishing is provided by a viscus fluid film at the interface of the anode and the electrolyte. Microelectropolishing occurs as a thin solid film is formed on the anode. In ideal microelectropolishing, the rate of film creation on the anode is the same as the rate of film removal into the electrolyte, thus providing a thin stable film. In jet type electropolishing, the viscous layer usually cannot be maintained, and the dominant process is microelectropolishing. The material is polished, i.e. anode material is removed, until the anode foil is thin enough for transmission electron microscopy.
The present invention provides a method for microelectropolishing a transmission electron microscopy nonhomogeneous multi-element compound foil having different elements which polish at different rates.